Cleaner Wrasse Self-Recognition Research
Cleaner wrasse fish (Labroides dimidiatus) have demonstrated signs of self-recognition and mirror exploration behavior in recent experiments. This marine fish, known for cleaning parasites from larger fish, was first reported to pass the mirror test in 2018.
Previous mirror mark tests involve animals reacting to an out-of-place mark on their body, seen in a reflection, as evidence of self-recognition. Species like chimpanzees, elephants, and dolphins have passed this test.
Updated Experimental Design Reveals Pre-Existing Self-Awareness
A new study by teams from Osaka Metropolitan University and the University of Neuchâtel modified the mirror test procedure.
Instead of introducing the mark after habituation to the mirror, fish were marked first, then presented with a mirror for the first time.
This change allowed fish to identify an unusual sensation on their body before seeing it visually in the reflection. Researchers observed that fish attempted to rub off the 'parasite' mark significantly faster, averaging about 82 minutes, suggesting a pre-existing self-awareness.
Novel Mirror Exploration Behavior Observed
After extended exposure to the mirror, some cleaner wrasse exhibited an unusual behavior: they picked up pieces of shrimp, carried them to the mirror, and dropped them. As the real shrimp and its reflection moved in sync, the fish followed the reflection closely, touching the mirror's surface with their mouths.
This behavior, termed 'contingency testing,' is interpreted by the scientists as the fish exploring the mirror's properties using an external object.
Similar behaviors have been observed in other species that did not pass the mark-based mirror test, such as pigs and manta rays.
Broader Implications for Self-Awareness
The study's findings suggest that self-awareness, previously considered unique to great apes, may be more widespread across vertebrates, potentially having evolved at least 450 million years ago with bony fishes.
Researchers indicate that these results could influence evolutionary theory, concepts of self, animal welfare practices, medical research, and artificial intelligence studies.